Wrong equirectangular panorama
Using your blend file (in blender 2.77a) the render was ok. Then using it as environment texture in world shader and viewport showed no pinching.

The problem seems to come from FSPViewer (sphere UV mapping).


EDIT:
Mapping an equirectangular texture on a UV sphere can't be done with UV unwrapping without pinching because of the tris at north and south poles. But you can use this setup: